diff --git a/mm/ksm.c b/mm/ksm.c
index d708b3e..9a68b0c 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1302,6 +1302,12 @@
 		slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list);
 		ksm_scan.mm_slot = slot;
 		spin_unlock(&ksm_mmlist_lock);
+		/*
+		 * Although we tested list_empty() above, a racing __ksm_exit
+		 * of the last mm on the list may have removed it since then.
+		 */
+		if (slot == &ksm_mm_head)
+			return NULL;
 next_mm:
 		ksm_scan.address = 0;
 		ksm_scan.rmap_list = &slot->rmap_list;